CALIFORNIA, U.S. - Uber has threatened to fire an engineer, who formerly worked with Google’s self-driving unit Waymo after Waymo alleged that the former executive stole trade secrets.

In its lawsuit against ride services company Uber, Waymo alleges that the former Waymo executive, Anthony Levandowski downloaded over 14,000 confidential documents before leaving Waymo to subsequently join Uber.

Uber is now reportedly threatening to fire the engineer, according to a court filing.

The high profile case pits two companies battling to dominate the fast-growing field of self-driving cars.

Levandowski faces allegations that the secrets he stole made its way into Uber's Lidar system, a key sensor technology in self-driving cars.

Last week, U.S. District Judge William Alsup in San Francisco issued an injunction ordering Uber to keep Levandowski away from all work involving the self-driving car technology.

This was to prevent him and all other employees from using the materials and to return them to Waymo by May 31.

Levandowski's lawyers said in a court filing that Uber had asked Levandowski to comply with the order to return Waymo documents or face possible termination.

Meanwhile, the lawyers reportedly requested the judge to modify his order so that Uber is not required to fire Levandowski if the engineer asserts his constitutional rights against self-incrimination and refuses to produce documents.

Uber has now said that it would appeal a judge's order rejecting its attempt to arbitrate Waymo's trade secret claims, a court filing revealed.

While Uber has not denied that Levandowski took Waymo documents, it has argued that it has not used any Waymo technology in its cars.